The last step of an asceptic terminal dispensing operation is to pass the product fluid through a filter. As the filtering is a critical-to-quality step, the filter must be tested once dispensing is complete to ensure the integrity of the filter media and thus the quality of the dispensed product. Testing of the filter media is performed by having a pressurized nitrogen source, through a burst line, apply pressure on the filter. Pressure above the filter, ie, on the same side of the filter media as the product fluid source, as well as pressure below the filter, ie, on the same side of the filter media as the dispensed product, is measured and recorded. Should the pressure below the filter suddenly increase, the integrity of the filter will be known to have failed. The filter must be kept wet during the integrity testing, or there is a risk of air-lock occurring which will thwart the testing. In one test method, Bubble Point Testing, the pressure at which the membranes fail and nitrogen bubbles are visible in transparent conduits downstream of the filter is provided by visual confirmation.
The integrity test is always performed to destruction. The burst pressure, or in a Bubble Point Test the pressure reading at which the membranes fail and nitrogen bubbles are visible downstream of the filter, for the filter is recorded. If the burst pressure, or bubble point, exceeds the minimum reading, the filter membrane can be considered intact for the fill. However, should the burst pressure be too low, or the pressure recorded below the filter be too high for a given burst pressure applied above the filter, the filter will be deemed to have been defective and the dispensed fluid will be deemed to have failed quality control. It is impermissible under regulations to simply then run the failed fluid through a new filter, as that is considered re-compounding. The loss of the dispensed product fluid may thus be extremely costly. And because the loss of the dispensed product fluid is so costly, producers must be sure of the quality of the dispensed product, and thus the integrity of the filters used in the final dispense step. Also of concern is the possibility of false failures, which will also result in loss of the dispensed fluid.
To reduce risk of losing the dispensed liquid, and with reference to FIG. 1, a secondary filter 2 is often included in the dispense procedure, where the secondary filter is serially connected directly to the primary filter 1. If the primary filter fails the destructive burst test, the secondary filter may be tested so that if it passes, the disposition of the dispensed product liquid is improved. However, as this testing takes place after removal of both filters 1 and 2 from the dispense line, and employs a common test method, ie, line, valving, N2 burst gas supply, burst regulator, are used for both filters 1 and 2. Differentiation between the filter integrity and the test method are not always clear as one cannot be sure that it was the test method equipment or the filters which are defective. The art lacks a system or method for allowing filter integrity testing of two filters serially connected along a dispense path.